1. Field of the Invention
The present invention relates to a three-dimensional image capturing device by which a three-dimensional shape of a measurement subject, which is to be measured, is captured by a time-of-flight measurement.
2. Description of the Related Art
Conventionally, there is known a three-dimensional image capturing device, in which distance measuring light beam pulses are radiated onto a measurement subject for a constant period and the reflected light beam pulses coming from the measurement subject are received and integrated by an imaging device such as a CCD. Namely, each photodiode of the CCD corresponds to each point on the surface of the measurement subject, and thus electric charge corresponding to the point is accumulated in the photodiode. Due to this, the shape of the surface of the measurement subject S is sensed.
In a conventional three-dimensional image capturing device as described above, if the device is constructed in such a manner that information, which is used for correcting a reflectance to improve the accuracy of the distance measurement, is sensed, it may be necessary to expand the output range of the imaging device, such as the CCD. However, merely expanding the output range of the imaging device will cause further difficulties in sufficiently improving the accuracy of the distance measurement.
Therefore, an object of the present invention is to improve the accuracy of the distance measurement, when sensing a three-dimensional shape of a measurement subject, without substantially expanding the output range of the imaging device.
According to the present invention, there is provided a three-dimensional image capturing device, comprising a distance measuring light beam irradiating processor, a first reflected light beam component sensing processor, a correction light beam irradiating processor, a second reflected light beam component sensing processor and a distance information calculating processor.
The distance measuring light beam irradiating processor irradiates a distance measuring light beam to a measurement subject. The distance measuring light beam is a pulsed beam. The height of the pulse changes with time. The measurement subject reflects the distance measuring light beam to generate a first reflected light beam pulse. The first reflected light beam component sensing processor receives the first reflected light beam pulse for a first sensing period to sense a first reflected light beam component. The correction light beam irradiating processor irradiates a correction light beam to the measurement subject. The correction light beam is a pulsed beam. The height of the pulse is constant. The measurement subject reflects the correction light beam to generate a second reflected light beam pulse. The second reflected light beam component sensing processor receives the second reflected light beam pulse for a second sensing period to sense a second reflected light beam component. The distance information calculating processor divides the first reflected light beam component by the second reflected light beam component to obtain the distance from the device to each point of the surface of the measurement subject.